WRX Electric turbo

[2000]

Originally Posted by serialk11r

A turbo doesn't do any heat conversion, it only picks up pressure left in the exhaust. Specifically on an Otto cycle gasoline engine, you have a little bit of extra pressure left in the cylinder when the exhaust valve opens, and this little burst of exhaust gas flow is where the energy is, and what a turbo aims to capture. This is why you can get more boost pressure than backpressure.
...

It's enthalpy. Calling it pressure is just as wrong as calling it heat because enthalpy for the exhaust gas is a function of both pressure and temperature (internal energy).

[serialk11r]

That's right, sorry about my often poor word choice.

One thing that is being researched is true exhaust waste heat recovery, with a heat exchanger in the exhaust stream but it seems at least a few years off.

[old greg]

Originally Posted by serialk11r

One thing that is being researched is true exhaust waste heat recovery, with a heat exchanger in the exhaust stream but it seems at least a few years off.

Shit, Smokey Yunick did that 30 years ago... sort of.

[azian_advanced]

Originally Posted by serialk11r

A turbo doesn't do any heat conversion, it only picks up pressure left in the exhaust.

i understand how a turbo works, i was simply puzzled how the author of the article (if you read it, you'd know) explains how exhaust gases are trapped and using the heat to power an electric turbocharger.

Originally Posted by Calum

wow, omg...

Please fellas, please look up turbine blades. Heat is very much so used in the process of converting the energy in the working fluid into mechanical energy. That mechanical energy is then used to turn something, in this case it'll be an electrical motor and/or a centrifugal compressor.

The steam plant I used to work on had steam entering the turbine at ~800 def F/600 PSIG and leaving, after being condensed, at 96 deg F/1 PSIA. Due to the relatively low pressure in that system, the blades were designed to get most of it's energy from heat, roughly 60:40. That plant generated 21,000 shaft HP at 108 RPM.

a single-stage turbine, like in automotive vehicles cannot be compared to a steam turbine, which have multiple turbine stages, when it comes to power generation. automotive turbochargers are primarily powered by the kinetic energy (fluid momentum) of the exhaust flow. there is no significant difference in pressure and temperature before and after the turbo. however, in a steam turbine, there are multiple turbine blade stages (think of the compressor blades in a jet engine) designed to exploit the expansion of the flowing steam from high enthalpy (high pressure & high temperature) to the outlet at a much lower enthalpy (pressure & lower temperature) as it passes through the turbine. the flow through steam turbines are also much slower when compared to automotive turbochargers. so what i'm trying to say is, automotive turbochargers do not rely on 'heat' as a primary source for mechanical power.

but back to the offtopic discussion on turbo-generator/electric-compressor idea, i don't think it'll work. generators require torque that exhaust-driven turbines simply cannot provide because there are internal rotors (magnets) that have much higher inertial-resistance than lightweight compressor wheels. as an alternative, keep the electric-compressor, just upgrade the alternator.

[old greg]

Originally Posted by azian_advanced

there is no significant difference in pressure and temperature before and after the turbo.

Sure about that?

[wcbjr]

Cult car?

[azian_advanced]

Originally Posted by old greg

Sure about that?

what you posted is the pressure ratio of the compressor outlet to the compressor inlet. not the turbine.

[2000]

I disagree. This is the compressor map.


That was the turbine map that old greg posted. If you look at the PDF, it's more clear.
http://www.turbobygarrett.com/turbob..._700382-12.pdf

[3MI Racing]

I don't think we'll see it until they need it to pass emissions without enough exhaust energy loss to hinder performance.
Cold start emissions are the problem and have been. So the composite FTP and/or ETC, pending regulation, is largely what would drive this in my opinion.
Actually the CAFE standards for CO2 emissions/fuel economy would drive it too.

I'm going to venture and guess that the next generation will be the FA16DIT with traditional turbo, as posted above.

[serialk11r]

Hmmm? How will it help emissions? Because they'll be able to tuck the turbine closer to the block?

This sort of setup would definitely help fuel economy though, that's for sure, however due to all the other electrical bits required to really make it worthwhile, I'd guess that until they start putting integrated motor-generator-starters on everything (which I can't see happening before 2016) they'll be sticking to traditional turbos.

[azian_advanced]

Originally Posted by 2000

I disagree. This is the compressor map.


That was the turbine map that old greg posted. If you look at the PDF, it's more clear.
http://www.turbobygarrett.com/turbob..._700382-12.pdf

i believe i was wrong then. thanks for posting. i learned something new today.

[3MI Racing]

Originally Posted by serialk11r

Hmmm? How will it help emissions? Because they'll be able to tuck the turbine closer to the block?

This sort of setup would definitely help fuel economy though, that's for sure, however due to all the other electrical bits required to really make it worthwhile, I'd guess that until they start putting integrated motor-generator-starters on everything (which I can't see happening before 2016) they'll be sticking to traditional turbos.

It would aid in having a catalyitc converter tucked close to the head wouldn't hurt performance like it does on a turbocharged system. The turbine could also be collecting energy all the time, stooring up for when you actuallly need it...assuming they wouldn't decouple it in certain areas of the map. Current turbos bring pumping losses with no benefit currently at low and light loads. In this case, the turbine 'generator' would still be storing power in these conditions. This power increase would/could be used to run more boost at lower RPM and improve Brake Specific Fuel Consumption (BSFC), since the turbo is 'spooled' by an electric motor.
They could even get a bit nutty and use this as the alternator for the car and then you loose the drag on the crankshaft from the alternator. This would really need some engineering time and testing to see if it would be worthwhile to do though...just spouting an idea.

An elementary case and point would be flooring the car at 2000 RPM:

current situation: fueling is added and timing is increased. Ignition starts early, more energy is lost in surface area to cooling (poor thermal efficiency), more pressure is building above the piston for a longer period (because of the advanced timing necessary, so loss of power). Overall, higher emissions, less power and poor BSFC.

potential situation: boost is added, via electric energy stored in light load conditions, and fueling is increased and timing is dialed back. This moves MBT closer to TDC and delivering a higher % of combustion energy into rotation (as opposed to building above and pushing the piston down as it approached TDC) and thermal efficiency is increased by having lower surface area for combustion. Essentially more of the fuel energy is converted to rotational energy via force from combustion and reducing energy expelled to the cooling system.

So, the better the BSFC usually indicates lower brake specific hydro-carbons, NOx, CO, COx, all those things that the EPA and CARB has us looking at

[serialk11r]

Oh, so let me make sure I'm understanding you correctly.

So it's obvious that giving electric boost for short periods of time is going to mitigate the need to stuff a lot of extra fuel (essentially, it gives you a greater range of loads that don't use boost), and this is obviously going to help efficiency.

Does the transient response of a turbo cause an emissions problem as well? When you floor it, the ECU starts increasing the air/fuel ratio immediately, even though the boost takes time to build up, so for like half a second (or more, depending on rpm) you're running much richer than you need to be.

As for the alternator thing, well, if there's already an electric motor attached to the crankshaft...no need for an alternator :P I imagine this sort of setup is going to be what manufacturers are aiming for in the future, turbo-generator, mild hybrid drive, variable boosting supercharger of some sort, downsized engine, exhaust waste heat recovery (to electricity), electric accessories, and DC-DC step down conversion to operate the low voltage electrical stuff.

[Calum]

Originally Posted by 3MI Racing

It would aid in having a catalyitc converter tucked close to the head wouldn't hurt performance like it does on a turbocharged system. The turbine could also be collecting energy all the time, stooring up for when you actuallly need it...assuming they wouldn't decouple it in certain areas of the map. Current turbos bring pumping losses with no benefit currently at low and light loads. In this case, the turbine 'generator' would still be storing power in these conditions. This power increase would/could be used to run more boost at lower RPM and improve Brake Specific Fuel Consumption (BSFC), since the turbo is 'spooled' by an electric motor.
They could even get a bit nutty and use this as the alternator for the car and then you loose the drag on the crankshaft from the alternator. This would really need some engineering time and testing to see if it would be worthwhile to do though...just spouting an idea.

An elementary case and point would be flooring the car at 2000 RPM:

current situation: fueling is added and timing is increased. Ignition starts early, more energy is lost in surface area to cooling (poor thermal efficiency), more pressure is building above the piston for a longer period (because of the advanced timing necessary, so loss of power). Overall, higher emissions, less power and poor BSFC.

potential situation: boost is added, via electric energy stored in light load conditions, and fueling is increased and timing is dialed back. This moves MBT closer to TDC and delivering a higher % of combustion energy into rotation (as opposed to building above and pushing the piston down as it approached TDC) and thermal efficiency is increased by having lower surface area for combustion. Essentially more of the fuel energy is converted to rotational energy via force from combustion and reducing energy expelled to the cooling system.

So, the better the BSFC usually indicates lower brake specific hydro-carbons, NOx, CO, COx, all those things that the EPA and CARB has us looking at

I wonder how much Fiat's multi air system could benefit this?